Your UI design is something first that your customers see when they are say browsing websites or shopping online. Your bounce rate is going to mean a lot as if users are not spending time on your website or product they can’t get in the position of buying it. Even the best product will not be able to sell itself with poor marketing and UI design in the 21st century.
People associate beautiful thing with quality and tend to be more open to interaction and trusting products that appear to look good. The psychology of this can be successfully implemented into the UI design process. Things here happen visually and the purchase of a product is somewhat a couple of clicks away. You do not want those clicks to be terrifying and hard.
Advertisement on the Internet has been massively popularized in the last couple of years and is proven to be a big industry. This is where UI is very important in terms of ad placement, positioning, meaning and quantity. Also, making and incorporating beautiful ads are something that you must do. You don’t want to spend all that money renting ad space when no one wants to click on your ads. They must be engaging, fresh and easy to look at when looking at the rest of the content of the website they are on.